The present invention relates to a swivel coupling and to a method of joining a swivel nut to a tail piece. More particularly, the present invention is directed to a swivel coupling including a swivel nut and tail piece of a tube and to a method of joining the swivel nut to the tail piece by deformation of a portion of the swivel nut.
There is a need to improve the reliability of swivel couplings used to couple high pressure hydraulic lines configured as tubes to fittings on devices such as hydraulic pumps and controls or other tubes. In the past, brazing has been used to make the connection between a tail end and associated hydraulic device, however, brazing can cause rippling in the bearing surface which can result in leakage.
In order to have a viable tight connection, it is preferable to have a flat face connection in which the tail piece has a flat end face which is directly abutted by the flat end face of the fitting of the device, with soft sealing being in a radial direction. Achieving a stable leak-proof interface between the abutting end faces has in the past been both expensive and difficult.
Normally, when using a swivel nut there are machining draft angles on mating surfaces which interferes with parallelism so that mating parts are not flush when they abut. This can result in leaks and bending moments during assembly that are detrimental to product performance. Normal crimping methods for attaching a swivel nut to a tail piece often results in non-uniform distortion and stress around the circumference, as well as localized high stress and deformations at locations between the individual crimping fingers of the segments. Consequently, coupling are unreliable with leakage tending to occur at high pressures.
In view of the aforementioned considerations, it is a feature of the present invention to provide a new and improved swivel coupling for joining a tube or a similar element to a fitting.
In view of this feature and other features, the present invention is directed to a coupling for joining an end of a tube to a threaded fitting, wherein the tail piece on the end of the tube has an end face and an outwardly extending radial shoulder spaced from the end face for coupling to a swivel nut. The swivel nut has a threaded portion and a collar portion formed about an axis. The collar portion extends from one end of the threaded portion and has a radial thickness less than the threaded portion. The collar portion also includes an end and an inwardly projecting radial shoulder spaced from that end, which inwardly projecting shoulder faces the outwardly projecting shoulder of the tail piece. In order to facilitate deforming the collar portion about the tail piece, the collar portion is inclined at an acute angle with respect to the longitudinal axis of the coupling.
A method for making the coupling formed about an axis for joining a swivel nut to a tail piece comprises providing the swivel nut with a threaded portion, from which threaded portion extends a radially deformable collar having an inwardly extending radial shoulder disposed adjacent an exterior frusto-conical surface inclined at an acute angle with respect to the axis of the coupling. The tail piece is provided with an outwardly extending radial shoulder to be abutted by the inwardly extending radial shoulder of the deformable collar. In accordance with the method, the swivel nut is slid over the tail piece with the inwardly extending shoulder of the swivel nut spaced from and facing the outwardly extending shoulder of the tail piece. The swivel nut is joined to the tail piece by pushing the swivel nut in an axial direction back against an inclined surface. Simultaneously, the tail piece is pushed in the same axial direction to cam the collar radially inward toward the tail piece. This places the inwardly projecting, radial shoulder on the collar into alignment with the outwardly projecting radial shoulder on the tail piece with an annular gap therebetween.
In both the swivel coupling and the method, the frusto-conical surface is inclined at an angle in the range of about 20 to about 30xc2x0 with respect to the axis of the coupling with the angle preferably being about 20xc2x0. In the method, the inclined surface against which the collar portion of the swivel nut is pushed is preferably inclined at the same angle as the frusto-conical surface defining the exterior surface of the deformable collar.